Zero,

From a BIAB perspective, the inversion of a chord is determined by the note that the bass plays (unless you have a single guitar or piano accompaniment). With this in mind, by entering the following chords you get,
  • C = root position
  • C/E = first inversion
  • C/G = second inversion

For a 7th chord,
  • C7 = root position
  • C7/E = first inversion
  • C7/G = second inversion
  • C7/Bb = third inversion

The same chords using Roman Numerals (and Nashville Notation) would be, if we assume that we are in the key of C major and we're talking about the C chord,
  • I = root position (in Nashville notation, 1)
  • I/III = first inversion (1/3, Nashville)
  • I/V = second inversion (1/5, Nashville)

This next bit is probably useless information but, to mind, it rounds off the story of chords When talking about the way in which inversions are notated in classical music, again if we're in the key of C major and talking about the C chord, we get,
  • I = root position
  • I 6/3 = first inversion (the 6/3 is usually written in superscript with the 6 sitting on top of the 3 and not a slash; often only the 6 is used and 3 is understood)
  • I 6/4 = second inversion (again, it's usually written with the numerals in superscript and 6 sits on 4)

I don't know if this information is useful but it might give you some insight. There are lots of different ways to notate chords

Regards,
Noel

P.S. C9 = C dominant 9th = C E G Bb D whereas C2 = C add 9 = C E G D

MY SONGS...
Audiophile BIAB 2025